Then she declared: “Now is the time for another step forward.” Despite criticism, she insisted that her new proposal for a deal with Brussels will “deliver decisively” what the electorate voted for in the 2016 referendum on EU membership.
In a statement Mrs May said: “The Cabinet meets at Chequers today to agree the shape of our future relationship with the European Union.
“In doing so, we have a great opportunity – and a duty – to set an ambitious course to enhance our prosperity and security outside the European Union and to build a country that genuinely works for everyone.”
She added: “We have already made good progress – on the text of the Withdrawal Agreement, by passing the EU Withdrawal Act and in agreeing an implementation period which gives people and business certainty. Now is the time for another step forward.
“We want a deal that allows us to deliver the benefits of Brexit, taking control of our borders, laws and money and by signing ambitious new trade deals with countries like the US, Australia and New Zealand.
“This is about agreeing an approach that delivers decisively on the verdict of the British people – an approach that is in the best interests of the UK and the EU, and crucially, one that commands the support of the public and Parliament.”
The Prime Minister was understood to be braced for marathon talks lasting at least 12 hours with the entire Cabinet at her countryside retreat in Buckinghamshire following growing concerns among Eurosceptics about her plans.
Mrs May claims her model, known as the Facilitated Customs Arrangement, offers the “best of both worlds” by combining some regulations in common as wanted by pro-Brussels ministers with demands from Brexiteers for digital technology to be used to set up fast and frictionless customs checks.
But Brexit backers in the Cabinet including Foreign Secretary Boris Johnson and EU Exit Secretary David Davis are expected to raise fierce objections to aspects they see as giving too much to Brussels.
Mr Johnson met Mr Davis and fellow Cabinet Eurosceptics Liam Fox, Andrea Leadsom, Michael Gove, Penny Mordaunt and Esther McVey at the Foreign Office last night ahead of today’s Chequers summit.
They were understood to be marshalling their arguments to launch a co-ordinated attack on the Prime Minister’s compromise proposals.
One source said: “The plan is little changed from the previous New Customs Partnership proposal that has already been rejected.”
Talks at Chequers are expected to begin around 10am today with the Prime Minister determined to win unanimous backing for her blueprint, meaning they could run into the early hours of tomorrow.
Ministers were instructed to arrive at the country house by 9.30am and expect to leave no earlier than 10pm.
She will ask them to approve both her compromise plan and the contents of a White Paper policy document due to be published next week setting out the Government’s vision for a future relationship with Brussels.
But one source close to a Brexiteer minister said last night: “We have tried to stay open-minded about this discussion, but the more details that have leaked out the more our hopes have been chipped away.”
Some ministers were also understood to be irritated by suggestions that Mrs May had given details of her plan to Germany’s Chancellor Angela Merkel before releasing them to members of the Cabinet.
Yesterday leading Brexit supporters including Tory MPs Jacob ReesMogg, Andrea Jenkyns, Marcus Fysh and Simon Clarke, along with the Democratic Unionist Party MP Ian Paisley, posted a video on YouTube urging the Prime Minister not to betray her manifesto promises.
They said: “We voted to take back control – taking back control means leaving the Single Market and the Customs Union. Please deliver on what people voted on.”
With tensions growing ahead of the meeting, Mr Davis was understood to have written to Mrs May warning her that her plan could be flatly rejected by Brussels.
He was said to be frustrated that the Prime Minister’s chief Brexit adviser Olly Robbins is refusing to acknowledge that the Government could simply be sent back to the drawing board by Brussels, wasting months of negotiating time.
The Prime Minister is to face fresh Commons battles over Brexit within the next fortnight.
Tory Commons leader Mrs Leadsom announced the Government’s Trade Bill and the Taxation (Crossborder) Trade Bill, two vital pieces of Brexit legislation drafted to prepare the statute book for Britain’s departure from the EU, will be debated the week after next.